. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 202 COMPARATIVE ANATOMY A large gland whicli,opens at the boundary between the inner and outer nasal cavities lies within the turbinal. Below the latter is the aperture of the lachrymal duct: this duct in some Reptiles opens on the roof of the pharynx (Ascalabota), and in others into the internal nostrils (Ophidia). The structure of the nose in Chelonians is very complicated and varied. In marine Chelonians it is divided into two passages, one above the other, and connected by means of a perforation of the septum. The
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative. 202 COMPARATIVE ANATOMY A large gland whicli,opens at the boundary between the inner and outer nasal cavities lies within the turbinal. Below the latter is the aperture of the lachrymal duct: this duct in some Reptiles opens on the roof of the pharynx (Ascalabota), and in others into the internal nostrils (Ophidia). The structure of the nose in Chelonians is very complicated and varied. In marine Chelonians it is divided into two passages, one above the other, and connected by means of a perforation of the septum. The comparative paucity of glands in the olfactory organ of Lizards and Snakes forms a marked contrast to the condition seen m Chelonians, the nasal organ of which is charac- terised by a great abundance of The extension downwards and back- wards of the olfactory organ is most marked in Crocodiles, iu correspondence with the growth forwards of the facial region and the formation of the palate ; its posterior part thus comes to lie below the brain and base of the skull. Each nasal chamber is divided posteriorly iuto two superim- posed cavities, the upper of which repre- sents the proper olfactory chamber, and is lined by sensory epithelium, while the lower functions as a respiratory portion only. Certain accessory air-chambers are connected with 'the nasal cavity. A large gland is present between the olfactory chamber and its investing bones, and opens into the nasal cavity. As in other Reptiles, there is only a single true turbinal, but ex- ternally to it lies a second prominence, which may be spoken of as a pseudo-turbinal. Fill. 161.—Diagram of the Olfactory Organ of a Lizard. (Longitudinal vortical section.) AN, IN, outer and inner nasal chambers ; +, tube- like connection between them; Ch, internal nos- trils ; P, papilla of Jacob- son's organ; Ca, aperture of communication of the latter with the mouth; MS, oral mucous mem- brane. Birds.—In all Bii'ds, as in Lizards,
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
